Translating device



M. c. HOPKINS May 24, 1927.

TRANSLATING DEVICE 7 Filed June 1925 2 Sheets-Sheet 1 INVENTOR /74/?c06[fla /rm:

ATTORNEY May 1927' M. c. HOPKINS TRANSLATING DEVICE FilBdJune 1925 2Sheets-Sheet 2 "mvENTbR Mica; (fla M45 WWW ATTORNEYS Patented May24,1927.

- UNITED STATES PATENT OFFICE.

MARCUS C. ITOPKINS'OF BROOKLYN, YORK, ASSIGNOR, BY DIRECT AND MIllSNEASSIGNMENTS, T O HOPKINS GOBPQRATION, A CORPORATIOH Olli DELAWARE.

TRANSLATING' DlEVICE.

Application filed June 6, 1925. Serial No. 35,425.

This invention'relates to electrical movements for translating varyingelectrical impulses'into mechanical motion, and aims particularly toprovide an electrical movement suitable for' use with radioloud-speakers, line-wire receivers and the like. This electricalmovement has special advantages 4 operation with a loud-speakerdiaphragm of the conical type, I have hereinafter described it inconjunction with a diaphragm of that type and particularly one somountedas to permit that free bodily movement of the cone which I have foundbest suited to give accurate tone production or reproduction.

Claims on the novel cone and its mounting, as disclosed in the presentapplication, are made in my co-pending application, Serial No. 34,255,filed June 1st, 1925. Other cones and other mountings can be used inconjunction with the electrical movement pole piece and-on each of themthere is claimed herein, but for best results there must be correctcoordination between the electrical movement and the vibratorydiaphragm. Due regard must be had to the weights of the several movingelements and to the magnitudes of their movements.

In'the preferred embodiment of my present invention the electricalarrangement is such that thevibration of the armature is of smallamplitude.

The electrical movement of the present invention includes a very rigidvibratory armature or reed, one end of which is se curely anchored, andthe other end of which is free to vibrate. -The free-end portion isnormally disposed midway between two electro-magnet poles-which are inturn secured to one pole of a strong permanent magnet, so that' bothelectro-magnet poles have the same normal polarity and normally exertequal and opposing forces on the free end of the armature. The twoelectromagnet poles are'those of a single soft iron by those mounted acoil through which the actuating or speech current circulates, therebycausing fluctuating differences of magnetic attraction between thearmature or reed and the electro-magnet poles. The structure may beregarded as including a polarizedreedwith 1ts free end positionedbetween opposing speech coils through eitheror both. of which themagnetic flux of said reed may pass. Current fluctuations in the speechcoils cause the armature or reed to vibrate correspondingly and thevibrations thus setup in the reed may be representative of and capableof being translated into sound waves.

I have discovered that distinctly improved to the armature canbe foundby trial.-

Under these conditions the amplitude of vibration of the diaphragm isless than the amplitude of vibration of. that portionof the armaturewhich is directly acted upon by the electromagnet. This is contrary tothe usual loud speaker. arrangement, wherein a step up actuation of thediaphragm is pro-,

vided for. My present arrangement is particularly suited for use with aconical diaphragm which is very rigid and light in weight and restrainedat the periphery as little as possible, so that the diaphragmarmature,the natural frequency may vibrate substantially as a'wh'ole instead ofbending in the manner of an ordinary diaphragm. Although the bestresults in radio and line wire receivers are realized only with a veryrigid, light and freely movin diaphragm, still, fair'results may be hadwith a diaphragm which could not be regarded as meeting thosequalifications, and the invention should, therefore, notbe construed aslimited in those respects except in'so far as such limits are includedin the appended claims. 4 e

Other features, characteristics and ad- Figs. 3, 4 and 5 are side, topand rear. views, respectively, of the electrical move-' ment used foractuatin the diaphragm;

Fig. 6 is a view part y in cross section of the electrical movement andon a larger scale than 3, 4 and 5;

Fig. 7 is a view partl' in cross section taken along the lines 7 of Fi6, and

Fig. 8 is a rear elevation of t e receiver with the ,electrical movementremoved.

The conical diaphra 1 is preferably of lar diameter, usua y more thannine inc es,,andygenerally is made wholly or in part of paper in orderthat it ma be of light we ht. The paper should stifi.

A long fi red paper of porous structure and free from loading will servewell, sizing should be of the fibers beand not of the sheet after it mod11' A layer of varnish and an fore fe tin has been it) or otherlikematerial applied to a finished .say, with little or no bending of thecone.

cone is likely to impair greatly its sound producing ualities.Brittleness in the cone is a desira le characteristic, rovided the paperhas at the same time su cienttoughness to withstand commercialtransportation and ordinary handling during use.

It has been my experience that paper se eral years old'is better thannew stock, presuma-bly because of an increased stiffening of the fibersdue to ageing. In anyevent, the paper used for the cone must be capableof being bent without breaking, in order that there may be formed in itthe one-or more peri heral creases or bends'on which I rely for eebodily movement of the diaphragm when in use.

In making the dia hra'gm illustrated a flat sheet of paper is rst cut toform a sector of the required radius and angle. This sector of paper isthen creased circumferentially at a lesserradius or radii to mark outthe line or linespnwhich the paper may be sharply bent to bring aboutthe results desired by me.

During theprocess of forming the flat sector into a cone those portionsof the paper sheet which are to form the supporting brim are pressed oneWay or' the other as-the case may be so that they-will assume theirproper plane. The cone is then glued along its radial joint. By formingthe complete cone this way the brim br circumferential corrugation isformed without any suljgtantial distortion of the paper such asj mightcause the main portion of the diaphragm to buckle in spots or becomeunequally stretched or tensioned.

As an alternative procedure I may cut the sector from the flat sheet ofpaper and glue it to form a cone, and then by means of a suitable toolcrease the cone near its edge and crowd the periphery forward ,until bybending sharply at crease 2 it snaps into the position shown in Fig. 2.Similar circumferential creasing on the lines 2 and- 2" will produce thetriple bend or corrugation of Fig. 1. From experience I have found thatwith a single bend as shown in Fig. 2 the forwardly flaring brim of thecone naturally takes up a position making the same angle to the verticalas does the main body of the cone. I consider this feature of importancebecause of the freedom from irregular strains in the. cone, and becauseit contributes to that freedom of bodily movement for the conewhich Ihave found to be so vital tothe most satisfactory sound production orreproduction.

.By virtue of a circumferential bend or plurality of bends and therigidity of the paper of which the diaphragm is made, the main portionof the diaphragm is enabled to vibrate substantially as a whole, that isto This results in much more accurate reproduction than-is possible witha diaphragm subjected to bending action. Best results are bad by havinga part, but not all, of,

the brim of the cone secured to a supporting structure, the remaining orinner portion of the brim being relied on for flexibility in giving tothe cone proper the needed support and restraint, but at the same timeallowing it to move axially much as if it were without support. Anyarrangement for supporting the diaphra m so that it'is capable of movingbodily with but little restraint may be employed instead of bending orcorrugating the peripheral portion of the diaphragm as. above described,but the arrangement shown is inexpensive, is attractive in appearance,and serves its purpose well.

The supportin phragm an electromagnetic actuating mechanism comrises aspun or pressed sheet metal memher 3 of frusto conical sha e having anoff set .rim with. a beaded structure for the diage 4 formed as shown toreceive the diaphragm. The metal 18 preferably cemented thereto but isenough er than the rim to provide the desired elastic support for thecone. The sheet metal member 3 is provided with a large central opening5 into which the electrical movement is removably inserted. A post 6,whidh may for t e electrical movement or openings as shown at 10, 11 and12 for the purpose of facilitating the passage of sound waves fromthe'inside of the instrument to the-unconfined air. The openings 10, 11and 1 2 may be of ornamental outline. The electrical movement comprisesa U-shaped permanent magnet 13, the two ends of which are slotted asindicated at 14 and 15. To one pole of the permanent magnet there issecured a soft iron pole piece 16. The pole piece 16 is secured to thepermanent magnet by means of a screw 17 Threaded studs 18 and 19constitute poles for the pole piece 16 and are adjustable'therein,toward and away from each other. Between the arms of the pole piece 16there is inserted a specially formed block 20 of insulating material,such as bakelite, having recesses of proper size to receive theelectromagnet coils 21 and 22, each of which surrounds one of the studs.

18 and 19. The central openings through the coils 21 and 22 are of theproper sze to fitthe unthreaded portions of studs 18 and 19. The coils21 and 22 should be securely gripped within the block 20 and if neces--sar they may be cemented in lace. The block 20 should make a snug fitlEetween the arms of the -pole piece 16, a d the unthreaded portions ofthe studs 18 and 19' should fit snugly within the openings through thecoils 21 and 22.- A very rigid soft iron armature or reed 23' is firmlybolted at one end to one pole of the ermanent magnet and its free end isnormal y situated midway between the ends of the poles formed bystuds18-"and 19. Normally the polarity of these oles is the same and they aresoadjusted that their magnetic attrac- .tions on the armature .are equaland opposing.

A rod 24is rigidly attached at one end to the armature 23 ata pointbetween its -secured end and that part which is disposed between theelectromagnet poles. The other endlof rod 24 is attached to the centerof the diaphragm by means of set screws 25. Rod 24 forms a connectinglink between and functionsto transmit the vibrations of the armature 23to the diaphragm 1'. In order to provide'a secure attachment to thecenter of the diaphragm, it isreinforcedbyv means Bf a pair of conicalwashers 26 secured together, with the-diaphra In between, by

. means of. a hollow rivet 2 through which the rod 24 extends.

Coils 21 and 22 are so wound that current passing one way willcause anattraction of armature 23 toward one of the electroma'gnet ales and vice-'versa. v

The diaphragm actuating mechanism, in-

cluding permanent magnet, armature, con necting link and coils forms aself contained unit which is mounted on a metal plate 28 through themedium of a wooden block 29 to which the permanent magnet is secured bymeans of a three-armed clamping plate 30, which: embraces the permanentmagnet, and a pair or wood screws 31. Plate 28 is secured to the sheetmetal supporting member 3 by means of four machine screws 32. A liftinghandle 33 is attached to plate 28 and affords a convenient means forcarrying the instrument about. c

Although I do not wish to be limited by any. thcor for the highlysatisfactory results obtained by me in sound reproduction through use ofthe apparatus above described as a loud speaker on radio and line wirecircuits, nevertheless, I.record my present ideas on the subject. Thearmature 23 beingof metal and relatively thick and stiff has a naturalvibratory period above audibility. The magnetic flux from that pole ofthe permanent magnet to which the armature is rigidly attached streamsacross the armature toward the other pole of the per manent magnet, andat or near the free or vibratory end of this armature that flux is splitinto two parts, one part going through soft pole 18 to the soft ironpoleishoe 16, and thence to the permanent ma'gnet. and the other partgoing throughthepole 19. Poles 18 and 19 are adjustable, and-bylongitudinal movement can. be so] positioned that themagnetio fiux isndrmallynsplit into two equal portions. This adjustment can be made atthe factory and-the poles can be 5 permanently clamped in their adjustedposition by suitable transverse bolts passing through the slotted poleshoe.

A current impulse through the speech coils 21 and 22 redistributesthemagnetic flux which streams outjof armature 23 into the'adjustable poles18 and 19 so that more than half of it goes to one pole, say pole 18.

,The armature 23 then moves toward pole 18 and by its movement decreasesthe air I gap thereby increasing the vflux to that 'suflicient to.permit fiexingof it, but the armature is so stiff and-is so supportedvat one end that ,it cannot strike the adjustable pole toward which 'itmoves. A current impulse through the-speech coils in the oppositedirection will produce '-a flexing of the armature toward pole 19," andvthe swinging armature is thus made to take up movements whichinfrequency and in vmagnitude represent the current variations thestructure in the speech coils. Bar 24 is rigidly attached to armature 23between the vibratory end and the supported end of that arma, ture. ThisI regard as an important innovation. There is a "gain in power but aloss in the magnitude of movement.

The exact point at which bar 24 can best be attached to armature 23 liesabout mid- 'way of the length of the armature, and

depends somewhat on the thickness and stiffness of the armature, and onthe weight and other characteristics of the diaphram to which bar 24 isri idly attached. The point can best be foun by trial.

The dia hragm which can best be used with this e ectrical movementis ofthe conical t pe, and preferably not less than 9" in iameter. Thefibrous material of which the cone is made should be light in weight andrelatively stiff. A porous pa er, the individual fibers of which are tigtly interlocked with one another and have been rendered stifi bfy sizingor ageing, will serve well. Sti ness or brittleness ac uired by fillingthe interstices between t e fibers of the paper, as with varnish, doesnot help. Free suspension of the cone so that it may move as :a wholethe coneasa whole that freedom of bodily movement that I have found sohi hly desirable, while at the same time In ing rugged enough'formerchantability.

By thus coordinating the diaphragm to the electrical movement a highlysatisfactory loud speaker can be obtained. Its tonal characteristics canbe varied some- I what. by changing the. weight or stiifness of thevibratory armature or reed, or by chan 'ngthe weight, size or thicknessof the brous cone. For best speech repro: duction the treble shouldf-beemphasized,

' and for best reproduction'of'music the base tones should beemphasized. As to the lower tones of themusical scale, my loud speakerpresents great advantage over any structure within my observation wheremovement of a small flatdiaphragm of the telephone type is amplifiedthrough a horn. My loud speaker is entirely free from the unpleasant orhorny-xtimbre of loudspeakers of the-horn type.

This invention is capableof considerable variation and modification'and'should not 1 beconstrued aslimited to the particular 1 of saidarmature.

ments of said armature.

1. In a translating device, the combina- I tion of a permanent magnet, aresilient reed supported at one .end by net and polarized thereby, twopoles of a speech magnet on opposite sides of the free end of saidresilient reed and between which the endof said reed projects,- andmeans for translating into sound the vibratory movements of said reed.

2.-In a translating'device, the combination of a permanent magnet, aresilient reed rigidly attached at one end to a poleof said magnet andpolarized thereby, two poles of aspeech magnet on opposite sides of thecentral plane of said ermanent magnet and between which the dice end ofsaid resilient reed projects, and means for translating into sound thevibratory m'ovementsof said reed. L

3. In a translating device, the combination of a U-shaped permanentmagnet, a resilient polarized vibratory armature supported at one end ona pole of said magnet and polarized thereby, a bifurcated pole shoeembracing the other end of said armature and between the two poles ofwhich the end of said armature projects, a speech winding 1n magnetizingrelation to said pole shoe and with'its axis perpendicular to the planeof said ma et, and means for translating into soun the vibratorymovements 4. In a translating device, the combination of a permanentmagnet, a polarized vibratory reed suplported thereon at one end andthrough whic the magnetic flux of said magnet passes longitudinally,v abifurcated pole shoe embracing-the other end of said armature andbetweenthe two poles of which the end of said armature-projects, aspeech winding on each sideof the free end ot said reed and inmagnetizing relation to said nole shoe, and aconical diaphragmopperatively connected to said armature to a pole of said mag--translate into sound the vibratory move- ,5. In a translating device thecombinetign of .a magnet, 11 vlbratory armature supported at one end bya and polarized thereby, a ifurcated pole shoe embracing the other endof said armature and betweenlthe two poles of which the end of saidarmature projects, a speech winding in magnetizing relation to said poleshoe, and atransmission. rod extending at right angles to the plane ofsaid ma et andconnected to said-armature interme 'ate its ends andsubstantially perpendicular thereto.

6. In a translating device the combination of a permanent magnet, apolarized vibrale of said 'magnet' tor-y reed rigidly' supported at oneend by a pole of'said magnet, a bifurcated pole shoe embracing the otherend of said reed and vibratory reed rigidly supported'at one end betweenthe two poles of which the end of said reed projects, a speech windingin magnetizing relation to each bifurcation of each pole shoe, and meansfor translating into sound the vibratory movements of said reed.

' 7. In a translating device the combination of a permanent magnet, apolarized by-a pole of said magnet and polarized thereby, a bifurcatedpole shoe embracing the other end of-said reed and between the two polesof which the end of said reed projects, a'speech winding in magnetizingrelation toeach bifurcation of said ole shoe, a transmission rodextending at right angles to the plane of said magnet, and a. diaphragmconnected to said rod and having its periphery positioned in a planeparallel to that of said permanent'magnet.

8. In a translatin device the combina tion-of a magnet, a vibratory reedsupported at one end by one pole ofsaid magnet and through which themagnetic flux of said magnet passes longitudinally, a pole shoe for theother poleofsaid magnet, said shoe having two poles on opposite sides ofthe free end of saidreed and between which said free end projects, aspeech-coil ,for'each shoe,po1e-, and.means for translating into soundthe movements of said a'rmaturepro ducedby-said speech coils; I y

9. In a translating device, the combina: tion of a magnet, a vibratoryreed rigidly supported at one .end by one pole of said magnet, a'poleshoe 'for the other pole of said magnet, said shoe'having two poles onopposite, sides of the central plane of said magnet and between whichthelfree end of said armature projects, a s eech coil' for other pole 0said magnet, said? shoe having each pole shoe, and means or translatingintosound the moy ements of said armature produced by-said speech coils.

10. In a translating devicethe combination of a permanent magnet, avibratory reed rigidl a softiron pole shoe forthe other'pole oftwo'opposed soft iron poles on opposite si es of the free end of saidarmature and between 'which' said end projects, a speech coil for eachshoe,

and means for, translating into sound the movements-of sald armatureproduced by said speech coils.

11-. In a translating device the combination ofv a (permanent magnet,aflexible arma-' 6o ture ri yattached atone end to one pole of saimagnet-said armature being, polars ized thereb'y a soft iron pole shoe.for the gaid magnet, said shoe'having supported at one end by one poleof sai magnet and polarized thereby,

two opposed soft iron poles on opposite sides of thefree end of saidarmature and between which said end projects, a speech COll for eachpole shoe and through which the magnetic flux of said polarized armaturemay divide, and means for translating into sound the movements of saidarmature produced by said speech coils.

12. In a translating device the combination of a permanent magnet, a.flexible armature rigidly attached at one end to one pole of saidmagnet,. a soft iron pole shoe for, the other pole of said magnet, saidshoe having two opposed adjustable poles on opposlte sides of-the freeend of saidarmature said magnet, said shoe having two opposed adjustablepoles on opposite sides of the free 'end' of said armature'and betweenwhich said free [end projects, afispeech coil encircling each shoe pole,and means, including a diaphragm, for translating'i'nto sound themovements of said armature'produced by said s ech coils.

14. na translating reed rigidly supported at one en a pole shoe adjacentthe other end of said reed, 'said shoehavin two poles on opposite sidesof the free" en of said reed and between which that free end projects,and a speech coil for each pole shoe, each 'of said coils being held instationary osition with respect to the pole'shoe an each .pole beingaxially rotatable in. the pole shoe andlongidevice the combina-' t on ofa permanent magnet, a olarized tudinally adjustable through itsspeechcoil.

15. In a translating device,'-the combination of .a U-shaped permanentmagnet, ,a polarized reed rigidly secured at one-end to end of said reeon opposite sides of the free end of said mod and between whichthat'free end rojects, .anda speech coil for each pole s oe,

each'of .said coils being'held in stationary position with; respect"tothe pole shoe, and

each pole being axiallly rotat 1e inthe pole shoe and lon itudina lyadjlistable through its speech 00' ture.

' i i MARCUS duos-Kins In testimony whereof I ailix my signs a pole ofsaid magnet and olarized thereby, a soft ironpole shoe ad acent theother said shoe having two poles

